Thermocouple safety pilot switch



1950 R K. ENGHOLDT muocou w smw mm SWI ICE Filed June 1'7, 1944 FNVENTOR.

PatentedJuly 1a, 1950 THEBMOCOUPLE SAFETY PILOT SWITCH Richard K. Enghold't, Milwaukee, Wis., assignor to Milwaukee Gas Specialty Company, Milwaukee, Wis, a corporation of Wisconsin I Application June 17, 1944, Serial No. 540,861

9 Claims. 1

This invention relates, in general, to an electric switch, and has particular relation to a thermocouple safety pilot switch.

The device which I shall describe hereinafter in connection with the drawing is particularly adapted for use with a thermocouple safety control device having an electromagnet connected in circuit with a thermoelectric generator and provided with an armature which is held attracted so long as the thermoelectric generator is heated, for example, by a pilot light for a main burner, and moves to retracted position when the pilot light is extinguished.

One of the main objects of the present invention is to provide an improved form of switch having switch operating means adapted to be pressed to move the armature to attracted position without closing the switch, and, thus, without establishing a supply of fuel for the main burner; the closing of my improved form of switch requiring not only release of the switch operating means, but, also, that the armature be held in attracted position by energization of the electromagnet by the heat, for example, of the pilot flame on the thermocouple.

Another object of the invention is to provide an improved form of switch of the class described of simple construction and composed of few parts;

also a device which operates effectively for the purposes set forth.

Another object of the invention is to provide a switch of the class described which in the form selected for illustration requires but one resilient contact carrying member, and does not need a pivoted armature carrying member separate from and in addition to the contact carrying member.

Another object of the invention is to provide, as a part of the switch operating means, an operating member mounted for swinging movement and adapted at one end for actuating the contact carrying member to move the armature to attracted position, the opposite end of the operating member adapted simultaneously to restrain engagement of the contacts until the armature is held in attracted position by the electromagnet and the operating member is released.

Another object of the invention is to provide a device of the character described which is adapted for installation with various types of burner and furnace constructions.

Further objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing.

In the drawing:

Figure 1 is a schematic view showing one application of a switch embodying the present invention;

Figure 2 is a top plan view of the switch as shown in Figure 1;

Figure 3 is a longitudinal sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a transverse sectional view taken on the line 4-4 of Figure 2;

Figure 5 is a fragmentary schematic view showing the contact carrying member in position with the contact carried thereby out of engagement with the cooperating contact and the armature in retracted position;

Figure 6 is a view similar to Figure 5, showing the contact carrying arm in position with the contact carried thereby in engagement with the cooperating contact and the armature in attracted position;

Figure 7 is a view similar to Figures 5 and 6, showing the operating member actuated to move the armature to attracted position, while restraining engagement of the contact carried by the contact carrying member with the cooperating contact until the armature is held in attracted position by the electromagnet and the operating means is released; and I Figure 8 is a fragmentary view similar to Figur 6, showing a modified form of auxiliary spring for the resilient contact carrying member.

In Figure 1 of the drawing a gas or other fuel burner of any suitable or preferred type is illustrated at Ill. The burner In may be the burner of a room or space heater, water heater, floor furnace, gas range, or any other burner. A gas or fuel supply pipe ll leads to the burner III for the delivery of gas or other fuel thereto-for example, through a mixing chamber 12 to which air is admitted in the usual way, as well understood in the art.

An electroresponsive valve I3, such as a solenoid or motor valve, is interposed in the fuel supply pipe II. The valve I3 is shown as comprising a valve body It and a hood I5 having any suitable power operated valve actuating means therein. A step-down transformer l6 supplies power for the operation of the valve It. This transformer comprises a line voltage primary H and a low voltage secondary I8. The primary I1 is connected to line wires l9 leading to any suitable source of current or power (not shown). The valve actuating means for the valve l3, the switch of the present invention, which is designated in its entirety at 20, and a thermostat, such as a room thermostat 2|, are shown connected in series circuit relation in the secondary circuit 22.

For purposes of the present disclosure it may be assumed that the valve I3 is of a character to be actuated to open position by closing of the circuit 22, and to be held in open position to supply fuel to the burner Ill as long as the circuit 22 is closed. The valve l3 may have spring means or other suitable means for actuating the valve to closed position to shut off the supply of fuel to the burner I when the circuit 22 is opened or otherwise disabled.

A pilot burner 23 is placed in juxtaposition to the main burner I 8, and provides a pilot light or flame 24 for lighting the main burner. A pipe 25, connected to the fuel supply pipe ll anterior of the valve l3, or otherwise as desired, supplies fuel for the pilot burner 23.

The particular form of switch selected for illustration comprises a supporting frame 28 having a lug 2l struck to position at right angles to the frame. The U-shaped magnet frame 28 is secured to the lug 21 by screws 28 which may permit adjustment of the magnet frame along the lug 21 for adjustment of the pole ends of the magnet frame toward and away from the armature 30. The shanks of the screws 29 are shown as passing through washers 32 which act as spacers between the lug 21 and the adjacent leg of the magnet frame. The coil 33 is wound around the legs of the magnet frame 28.

A thermocouple, indicated at 35, is placed in position so that the hot junction 35 thereof will be heated by the pilot flame 24 as long as the pilot flame is burning. While the thermocouple and leads therefor are shown as similar to the thermocouple and leads more fully disclosed in Oscar J. Leins Patent No. 2,126,564, issued August 9, 1938, it is to be understood that the thermocouple and its leads may be of any other suitable or preferred form within the scope Of the present invention.

For the purpose of the present description, sufiice it to state that the particular thermocouple selected for illustration comprises an outer tubular metallic thermocouple element and an inner metallic thermocouple element of different thermoelectric characteristics. The thermocouple elements are joined to form the hot junction 35. An outer tubular lead conductor 31 is connected to the outer thermocouple element, for example, through a sleeve 38. The inner lead conductor 39, enclosed by and insulated from the outer tubular lead conductor 31, is connected to the inner thermocouple element. The inner lead conductor 33 is connected in circuit with one side of the coil 33, and the outer lead conductor 31 is connected in circuit with the opposite side of the coil 33, for. example, through a conductor 48, as shown in Figure l.

The resilient contact carrying member 42 is fixedly secured or anchored at one end to the frame '28, for example, by a rivet 43. The member 42 constitutes an electric conductor for the circuit22, one of the conductors of the circuit '22 being connected, for example, to the fixedly anchored end of the member 42, and a continuation of such conductor of the circuit 22 being connected to a lug 44 on a conducting strip 45 to which a stationary contact 48 is secured. The conducting strip 45 is positioned between a pair of insulating strips 41, and the contact 48, on the outer end of the contact carrying member 42, moves into and out of contact with the contact 43 and between the inner insulating strip 41 and a third insulating strip 43. The insulating strips 4'! and 43 and conducting strip 45 are secured together and to the adjacent end of the frame 25, for example, by rivets 50, or otherwise as desired. The armature 30 is also fixedly secured to the contact carrying member 42, for example, by soldering, or otherwise as desired.

The resilient contact carrying member 42 tends, by reason of its own resilience, toward a first position engaging the insulating strip 49 which serves as a stop for limiting movement of the free end of the member 42 in this direction. A pin 52 on the contact carrying member 82 operates in an opening in the strip 49 to guide the free end of the member 42 and prevent lateral displacement of the contact 48 on the member 52 relative to the contact 48.

In the particular form of device illustrated in Figures 1 through '7 of the drawing, the contact carrying outer end of th resilient member 42 is shown as terminating in an integral laterally elongated part having integral auxiliary spring strips 55 parallel with the member 62, and with one of the auxiliary spring strips 55 on each of the opposite sides of the member 42. These auxiliary spring strips 55 are secured at 56 to lugs 51 integral with the frame 28, and the auxiliary spring strips 55 are bowed as shown in Figures 3, 5, 6, and '7 to present an additional or auxiliary force which tends to move the contact carrying member 42 toward the insulating strip or stop 49 with the contact 48 out of engagement with the contact 85.

An operating member is mounted at 6! for swinging or pivotal movement, and is adapted at one end 62 to engage and move the contact carrying member 42 in a direction to move the armature 30 from its retracted position shown in Figure 5 to its attracted position shown in Figures 6 and '7. The opposite end of the member 80 has a portion 63 which extends around the adjacent end of the contact carrying member 42 to engage this member 42, at 54, simultaneously to restrain engagement of the contact 48, carried by said member, with the contact 45 as the member 60 is swung in a clockwise direction about its pivot from the position shown in Figure 5 to the position shown in Figure 7, and until the armature 30 is held in attracted position by the electromagnet and the operating member is released.

A push button is provided for swinging the member 60 about its pivot 8|, from the position shown in Figure 5 to the position shown in Figure '7. The button 65 extends out through an opening in the adjacent member 68 for engagement by the hand or finger, as shown in Figure 7, A tension spring, shown more or less schematically at 10, may be provided for holding the adjacent end of the member 60 yieldingly against the inner end of the button 65 and for holding the button 55 in its outwardly projected position, as shown in Figures 5 and 6, and for returning the button to this position.

In the modification illustrated fragmentarily in Figure 8 I have shown an auxiliary tension spring I2, instead of the auxiliary spring portions 55, for presenting the additional force which tends to move the contact carrying end of the contact carrying member toward the insulating strip or stop 49, with the contact 48 out of engagement with the contact 48.

To start the operation of the system shown in the drawing, the following sequence is followed:

The button 65 is engaged with the hand or finger and pressed inwardly, and by its engagement with the adjacent end of the operating member 60 swings this member 50 clockwise about its pivot 6! from the position shown in Figure 5 to the position shown in Figure '7. The adjacent. end 82 of the member 80 engages the resilient contact carrying member 42, and moves the portion of the member 42 adjacent the armature 33 toward the electromagnet and the armature It to attracted position. The opposite end oi. the member ll, by its engagement with the opposite side of the contact carrying member 42 at 64 (Figure '1), simultaneously holds the contact carrying end of the resilient member 42 against movement toward the contact 40, thereby restraining engagement of the contact 48 with the contact 48 until the armature 30 is held in attracted position by the electromagnet and the operating button 65 is released.

Upon ignition of the pilot burner 23, the pilot flame 24, by heating the hot junction 26 of the thermocouple I5, energizes the electromagnet sufilciently to hold the armature 30 in attracted position. When the button 5 is released with the armature 30 held in attracted position by the electromagnet, the spring HI returns the button to its outwardly projected position and releases engagement of the member 60 with the member 42, at 64. The contact carrying end of the contact carrying member 42, having been held under tension with the contact 48 out of engagement with the contact 46, snaps into position with its contact 48 in contact with the contact 46. Assuming that the circuit 22 is also closed at the thermostat 2|, the valve I3 is opened by completion of the circuit 22 for the supply of fuel to the main burner III, which is then ignited by the pilot flame 24.

From the foregoing it will be apparent that the switch 20 closes the circuit 22 not by the inward movement of the button 65 or by the armature resetting operation, but only if and after the armature 30 is reset and held in attracted position by the electromagnet and the button 65 is released. The closin of the circuit 22 and opening of the valve B for the supply of fuel to the main burner is thus prevented except when the pilot burner is ignited so that it will ignite the fuel which is delivered to the main burner.

If the heat of the pilot flame on the thermocouple has not generated sufficient E. M. F. to hold the armature 30 in attracted position, the resilient contact carrying member 42 will, by reason of its own resilience and/or the resilience of the auxiliary spring means, where such auxiliary spring means is employed, return the member 42 to position, with the armature 30 retracted and the contact 48 out of engagement with the contact 46, the switch remaining open and the valve l3 remaining closed.

If, after the parts are set, as shown in Figure 6, and the pilot burner is lighted to hold the parts in the positions shown in this figure, the pilot flame is extinguished, the armature is released. The resilient contact carrying arm 42 then moves from the position shown in Figure 6 to the position shown in Figure 5. This moves the armature 30 to retracted position, and separates the contact 48 from the contact 46, thus opening the circuit 22 and closing the valve I3 to shut off the supply of fuel to the main burner.

The embodiment of the invention shown in the drawing is for illustrative purposes only and it is to be expressly understood that the drawing and the accompanying specification are not to be construed as a definition oi the limits or scope of the invention, reference being had to the appended claims for that purpose.

I claim:

1. In a switch of the class described, in combination, a fixed contact, a resilient contact carrying member having a movable contact thereon and tending by its own resilience to move the contact thereon out of contact with said fixed contact, an armature on said contact carrying member, an electromagnet for said armature, an operating member operable to move only the part of said contact carrying member adjacent to the armature thereon in a direction to move said armature to attracted position relative to said electromagnet, and means on said operating member and cooperating with said contact carrying member to restrain accompanying movement of the part of said contact carrying member adjacent to the contact thereon whereby to prevent contact of the contact on said contact carrying member with said flxed contact until said armature is held in attracted position by said electromagnet and said operating member is released.

2. A switch according to claim 1 wherein the contact carrying member is in the form 01' a resilient strip anchored at the end opposite the end having the movable contact thereon to a supporting frame and wherein the end of said resilient strip having the movable contact thereon has a laterally elongated part provided with auxiliary spring strips parallel with said contact carrying strip, each of said auxiliary strips being integral at one end with said contact carrying strip and secured at their opposite ends to said supporting frame, said auxiliary strips presenting additional force which tends to move the movable contact on said contact carrying strip out of contact with said fixed contact.

3. A switch according to claim 1 wherein the operating member is disposed on one side of said contract carrying member and the means on said operating member for restraining accompanying movement of the part of said contact .carrying member adjacent to the contact thereon cooperates with the opposite side of said contact carrying member.

4. A switch accordin to claim 1 wherein the operating member is pivoted between its ends for engagement on one side of said pivot with the contact carrying strip in proximity to the position of the armature thereon.

5. A switch according to claim 1 wherein the operating member is pivoted between its ends for engagement on one side of said pivot, with the contact carrying strip in proximity to the position of the armature thereon and wherein there is a push button cooperable with said contact carrying strip on the side of its pivot at which said armature is disposed.

6. A switch according to claim 1 wherein the operating member is pivoted between its ends for engagement on one side of said pivot, with the contact carrying strip in proximity to the position of the armature thereon and wherein there is a push button cooperable with said contact carrying strip on the side of its pivot at which said armature is disposed, and spring means for holding the adjacent end of said operating member against the adjacent end of said button and said button in its outwardly projected position.

7. In a switch of the class described, in combination, a resilient contact carrying member tending by its own resilience to move to a first circuit controlling position, a contact on one part of said contact carrying member, an armature on another part of said contact carrying member, an electromagnet for said armature, and means operable to move only the part of said contact carrying member adjacent to the armature thereon in a direction to move said armature to attracted positions relative to said electromagnet 7 and for, at the same time, restraining the part of said contact carrying member adjacent to the contact thereon against accompanying movement.

8. A switch according to claim 7' wherein the resilient contact carrying member comprises a spring strip tending by its own resilience to move to a first circuit controlling position when the electromagnet is denergized, said spring strip having a portion thereof on which the contact is carried tending to a second circuit controlling position when the electromagnet is energized and the armature on said contact carrying member is held attracted to the electromagnet.

9. In a switch of the class described, in combination, a resilient contact carrying member, a contact on one part of said contact carrying member, an armature on another part of said contact carrying member, an electromagnet for holding said armature in attracted position, said resilient contact carrying member tending by its own resilience to move to a first circuit controlling position when the electromagnet is deengergized, the contact carrying portion of said resilient contact carrying member tending to move to a. second circuit controlling position when the armature is held attracted to the electromagnet, operating means operable to move the armature carrying part of said resilient contact carrying member to position in which the armature is held attracted by said electromagnet, and means REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 621,739 Baumann Mar. 21, 1899 1,149,325 Barnum Aug. 10, 1915 1,267,603 Stirling May 28, 1918 1,507,643 Walimann Sept. 9, 1924 1,560,440 Tritle Nov. 3, 1925 2,096,546 Jackson Oct. 19, 1987 2,119,450 Trautner May 31, 1938 2,132,057 Thornbery et ai. Oct. 4, 1938 2,164,694 Betz et a1. July 4, 1939 2,165,801 Kronmiller July 11, 1939 2,183,827 Thornbery Dec. 19, 1939 2,198,453 Mantz Apr. 23, 1940 2,237,577 Ray Apr. 8, 1941 2,245,834 Sparrow June 17, 1941 2,337,001 Ray Dec. 14, 1943 

